Rocker arm for overhead valves

ABSTRACT

A rocker arm assembly for overhead valves is composed of one rocker arm mounted on a tubular portion of a second rocker arm extending at a right angle to the camshaft, flat-faced cam followers on one end of each rocker arm, and a flat-faced ball movably mounted on the other end of each arm and engaged with a valve stem.

United States Patent [7 2] lnventors Ernst Schmidt;

Julius Liebel, Nurnberg, Germany [21] Appl. No. 794,106 [22] Filed Jan. 27, 1969 [45] Patented Jan. 19, 1971 [7 3] Assignee Maschinenfabrik Augsburg-Nurnberg,

Aktiengesellschaft Nurnberg, Germany [54] ROCKER ARM FOR OVERHEAD VALVES 1 Claim, 4 Drawing Figs.

[52] U.S.Cl 123/9027, 74/55,74/569; 123/9 0.44 [51] lnt.Cl FQ111/18, F011 1/04 [50] FieldofSearch 123/90, 1910, 1931-l; 74/55, 569

[5 6] References Cited UNITED STATES PATENTS 1,076,903 10/1913 Mitchell 123/90 1,515,201 11/1924 Hewitt 123/90 1,988,018 l/1935 Peterson 123/90 2,158,272 5/1939 Chilton l23/90X 2,410,411 11/1946 Gregory 123/90 2,713,855 7/1955 Witzk-y 123/90 3,362,250 1/1968 Bradley 74/569 FOREIGN PATENTS 642,843 5/1928 France 123/90 1,001,927 10/1951 France 123/90(H) 288,749 4/1928 Great Britain.... 123/90(D) 548,634 10/1942 Great Britain.... 123/90(H). 720,432 12/1954 Great Britain.... l23/90(H) 405,601 8/1943 ltaly 123/90(A) 217,037 1/1942 Switzerland 123/90(A) Primary Examiner-A1 Lawrence Smith Attorneys-Francis D. Stephens and Hugo Huettig, Jr.

ABSTRACT: A rocker arm assembly for overhead valves is composed of one rocker arm mounted on a tubular portion of a second rocker arm extending at a right angle to the camshaft, flat-faced cam followers on one end of each rocker arm, and a flat-faced ball movably mounted on the other end of each arm and engaged with a valve stem.

PATENTED JAN] 91911 SSS-SL061. SHEET-10F 2' INVENTORS Ernst Schmidt Julzus Lzebel PATENTEDJAMSIISTI V sum 2 DP 2 INVENTORS Ernst Schmidt Julia; Liebel ROCKER ARM FOR OVERHEAD VALVES This invention relatesto a valve control for a rocker arm in an overhead valveinter nal combustion engine in which the overhead camshaft lies parallel to the rows of valve stems. This invention is particularly useful for a high-speed aircooled high-capacity fuel injection engine.

The valve rocker arms in conventional engines directly engage both thecam on the camshaft and the valve stem. These rocker arms for the valves are, in this case, very short for structural reasons so that the rocker arms describ e small arcs during their movement. Consequently, if the axis of the rocker arm lies parallel to the camshaft axis, a thrust is produced which acts transversely on the valve stem and which leads to a premature wear and tear on the slide bearing guiding the valve stem as well as premature wear and tear on the valve itself. If, however, the axis of the rocker arm is arranged at a right angle to the valve stem axis, thenthis produces very unfavorable movement conditions on the otherend of the rocker arm on thecam.

The object of this invention is to produce a simple manner to eliminate the aforesaid disadvantages and also to produce a valve'control which permits adequate cylinder head cooling and which permits the positioning of the fuel injection noule and, if need be, an additional spark plug in such a way that the flow of cooling air is insignificantly disturbed and also that the fuel injection nozzle, as well as the spark'plug, if used, are easily accessible for maintenance purposes.

lngeheral, these objectsof the invention are obtained by combining the following featuresi a. One rocket arm is positioned on a tubular center portion of the other rocker arni and with the axis of the center portion extending'at a right angle to the camshaft axis.

b. Each rocker arm hasjone end engaged with the cam by means of acam follower which isflattened on its cam a c. The other end of the rocker arm engages the valve stem through a flat side on a ball which ism'ovably mounted'in aplug in the rockerarm.

This construction produces operating conditions and wearand-t earconditions as .exist in mushroom tappets. The cam follower which has one side flattened and bears on the cam has a linear contact identical with that of a mushroom tappet and thisis maintained bythe movability of the cam follower in every rocker arm position. The result is very little wear and tear onthe cams and the contact surfaceof the rocker arm and also makes possiblethe use of a spherical cam. Because of flattened ball on the other end of the rocker arm, there is also produced between the valve stem and rocker armfand in every position ofthe rocker arm, a satisfactory surface contact which'also'has very good lubricating conditions, that is, it always n'esa sizable film of lubricating oil so that the component forces exerted on the valve stem are especially small. The lifespan of the valve guide bearing isthus increased to a considerable extent. It is further of especial advantage in that, because of the crosswise arrangement of thevrocker arms, it is possible to make the arms longer. This lengthening of the arms permitsthem to swing in larger arcs whichgreatly reduces the comp o nent forces on the valve stem. Finally, this construction permits theindividual parts to be easily removed as well as the easy adjustment of theparts interplay. Also, the installation and removalof each valve control arrangement is very simple. The valve control. can be separately removed from each cylinder without changing in any way whatsoever the valve adjustmentassuch.

In the prior art, insofar as feature (a) is concerned, a valve eontrol for internal combustion engines has been used for overhead valves operated by a camshaft extendingparallel to the plane of the valve stems and' having rocker arms in which eachsingle rocker arm is mounted on the tubular center portion of the other rocker arm. However, in such construction, the camshaft is positioned in the crank case and therefore is a push rod system.

The aforesaid feature (b) has been used only with a conventional rocker arm valve control.

Feature (c) has been used for a specific push rod valve control, whereas this invention provides a lubricant film between the rocker arm and thevalve stem.

The above prior art features are therefor features which have been heretofore always used'for other individual require ments and havenot been brought together in the combination of this invention. The aforesaid substantial advantages of this invention are gained only by the combination of these features.

The means by which the objects of this invention are obtained are described more fully with reference to the accompanying drawings in which:

FIG. 1 is a top plan view of the overhead valve assembly;

FIG. 2 is a side elevational view taken on the line 2-2 of F IG. 1;

FIG. 3 is a cross-sectional view taken on the line 3-3 of FIG.

1; and

FIG. 4 is a cross-sectional view through the cam and cam follower as taken on the line 4-4 in FIG. 3.

As shown in FIGS. 1 and 2, the camshaft 1 carries cams la and lb. Cam 1a actuates rocker arm 2 which is composed of two arm portions 2a and 2b. Rocker arm 2 has a third arm portion 2c mounted on the tubular center portion 30 of the other rocker arm 3 with the axis of rocker arm 3 extending at a right angle to the axis of cam shaft 1. Rocker arm 3 has arm portions 30 and 3b which are clamped on the center tubular portion 30 by means of screws 3d.Rocker arm 3 is mounted on bolt 10. I

Arm portions 2a and/or 3a are each provided with a cylindrical recess or cavity 4, as shown in FIGS. 2 and 3, in which is seated a cam follower 5 having a flat side 5a, The cam follower 5 has a hollow bore 5b for purposes of saving weight. The opening center angle of cylindrical cavity 4 is less than FIG. 3, and embraces carn follower 5 to prevent the follower from falling out.

The flattened follower 5 has collars 50, FIGS. 2 and 4,each one having a recess 5d into which securing pins 6 are positioned. The two rocker arm portions 2b and/or 3b have at their ends 2d and/or 32 cylindrical openings 22 and/or 3f. The curved ends 2d and/or 3e have slots 2f and/or 3g which are clamped together by screws 2g and/or 3h, FIG. 1. Plugs 7 with hexagonal wrench receiving sides 7a are mounted in the openings 22 and/or 3f. The lower ends of plugs 7 have similar sockets 7b for the reception of the ball spherical member 8 having a flat side 8a which engages with play the circular head 9a of the valve stem 9. v

The operation of this assembly is as follows: t t

The followers 5 have their flat sides 5a engaging the cams la and/or lb exactly in the .manner of mushroom tappets. This results in a linear contact which, because of the elasticity or elastic deformation of the material, becomes a surface contact having relatively low surface pressure. This, however, is only possible since the follow 5 can turn in the cylindrical recess 4 in the rocker arm portions 20 and/or 311, In a conventional construction without a movable cam follower, it would be necessary that the end of the rocker arm is also formed as a cam or, in other words, curved. This would theoretically produce a dotlike contact which, in practice because of the elastic deformation of the material, would lead to an infinitesimal circular contact surface which would cause an extraordinarily larger specific surface pressure with resulting In contrast thereto, this invention creates very slight surface pressure because of the movable cam. follower despite thefact that the rocker arm operates directly on the cam. The same is true for the two arm portions 2b and/or 3b which act directly on the valve stems. in this case, we have inserted a known flatsided ball or spherical member 8 between the arm 2b and/or 3b and the valve stem 9. Thus, during the operation of the valve drive, there is no contact of the rocker arms 2b and/or 3b on the end surfaces of the valve with dangerously high surface pressure of the valve with dangerously high surface pressure because of the movement or displacement of themocker arm. Above all, because of the short are around which the arm portions of the rocker arm are moving or swinging and because of the small surface pressure which results from a good film of lubricating oil, there are no strong component forces which act on the valve guide bearing and which would cause rapid wear and tear of the guide bearings in conventional constructions. The flattened sides 8a of the members 8 slide in this invention back and forth on the end surfaces of the valve stems because of the arcular movements of the rocker arms and without being subject to the dangerous component forces exerted on the guide bearings.

Theflat cam followers 5, FIGS. 3 and 4, are inserted into the cylindrical recesses 4 by turning the followers 5 90. When this is done, it is very easy to position the follower 5 into recess 4. Then when the follower 5 is turned to its original position, it is impossible for it to fall out since the opening center angle is less than 180. Collars 50 adjacent the ends of followers 5 prevent the followers from sliding out in an axial direction while safety pins 6 positioned in the recesses 5d of the collars 5c prevent the followers from turning back into the position into which they were originally inserted.

The flat-sided spherical members 8 are partially enclosed and held in the plugs 7 by a slight constriction of the plug opening and are thus prevented from falling out downwardly. By means of this, it is impossible, even during valve flutter,

because of the racing of the engine and the lifting of rocker arms 2 and 3 from the cams la and/or 1b engaged therewith for either the cam follower 5 or the spherical member 8 to fall out or to jam.

Having now described the means by which the objects of the invention are obtained,

We claim:

1. A rocker arm valve control for an overhead multivalve internal combustion engine including cylinders comprising overhead valve stems, an overhead camshaft extending parallel to the plane of the valve stems.

a. a first rocker arm 3 having a tubelike center portion 30 having its axis at a right angle to the axis of said cam shaft, and a second rocker arm 2 for .the same cylinder mounted on said center portion;

b. a cam follower 5 turnably mounted on an end 2a, 3a of each arm 2, 3 and having a flat side 5a bearing in linear contact on its respective cam; and

c. a plug 7 having a recess mounted in the other end 212, 3b of each arm, a spherical member 8 movably positioned in said recess, and a flat. side on said member 8 bearing on its respective valve stem. 

1. A rocker arm valve control for an overhead multivalve internal combustion engine including cylinders comprising overhead valve stems, an overhead camshaft extending parallel to the plane of the valve stems, a. a first rocker arm 3 having a tubelike center portion 3c having its axis at a right angle to the axis of said cam shaft, and a second rocker arm 2 for the same cylinder mouNted on said center portion; b. a cam follower 5 turnably mounted on an end 2a, 3a of each arm 2, 3 and having a flat side 5a bearing in linear contact on its respective cam; and c. a plug 7 having a recess mounted in the other end 2b, 3b of each arm, a spherical member 8 movably positioned in said recess, and a flat side 8a on said member 8 bearing on its respective valve stem. 